CA1171699A - Low mn alloy steel for cryogenic service - Google Patents
Low mn alloy steel for cryogenic serviceInfo
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- CA1171699A CA1171699A CA000357401A CA357401A CA1171699A CA 1171699 A CA1171699 A CA 1171699A CA 000357401 A CA000357401 A CA 000357401A CA 357401 A CA357401 A CA 357401A CA 1171699 A CA1171699 A CA 1171699A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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Abstract
ABSTRACT
A ferritic cryogenic steel which has a relatively low (about 4-6%) manganese content and which has been made suitable for use at cryogenic temperatures by a thermal cycling treatment followed by a final tempering. The steel include 4-6% manga-nese, 0.02-0.06% carbon, 0.1-0.4% molybdenum and 0.3% nickel.
A ferritic cryogenic steel which has a relatively low (about 4-6%) manganese content and which has been made suitable for use at cryogenic temperatures by a thermal cycling treatment followed by a final tempering. The steel include 4-6% manga-nese, 0.02-0.06% carbon, 0.1-0.4% molybdenum and 0.3% nickel.
Description
~ 7 ~
LOW Mn ALLOY STEEL FOR CRYOGENIC SERVICE
BACKGROtlND OF THE INVENTION
Field of the Invention . . _ This invention relates to an alloy steel composition, in particular, a low-maganese alloy steel composition suitable far cryoqenic applications and a method for preparing the com-position.
nescription of the Prior ~rt Due to dwindling natural gas supplies in this and other countries there is considerable interest in containment vessels for safely transporting liquefied natural gas (LNG) by ship and other transport. Because the boiling temperature of natural gas is in the cryogenic tgenerallY below about -80 to -100C) range, LN~. containers must be designed to avoid breakage due to pres-sure and crack development over a broad temperature range.
There is also the danger of a catastrophic explosion or fire, should the containment vessel fail.
At crvogenic temperatures, ordinary steel alloys lose much of their resilence and become very hrittle. A denominator of the steel alloys commonly specified for structural applica~
tians at LN~, and lower temperatures is a relatively high content of nickel. The nickel contributes significantly to good low tem~erature properties; but, is a relatively scarce metal and, thus, adds substantially to the cost. Recently, lower (5-6%) Ni steels have been introduced to reduce cost.
Storaqe systems for other liquefied gases, particularly nitrogen, oxygen, and liquid air, are also a significant market for cryogenic alloys. This market is different than that for LNG in that the safety standards are less stringent and a larger 7 ~
number of alloys compete with more emphasis placed on mate~ials cost.
Of the common alloying elements in steels, manganese is considered the most attractive substitute for nickel. Man-ganese ;s readily available, and, thus, relatively inexpensive, and has a metallurgical similarity to nickel in its effect on the microstructures and phase relationships of iron-based alloy~. Therefore, there has been considerable interest in the potential of Fe-Mn alIoys for cryogenic use.
Fe-12Mn (12% manganese) alloys have been made tough at 77K (-196C) by several methods: (1) a cold work plus temper-inq treatment, (2) controlled cooling through the martensite transformation, and (3) the addition of a minor amount of boron. However, although manganese is less expensive than ni~kel, it also adds to the cost of the steel, and, therefore, a lower manganese content would be advantageous.
Statement of the Objects Therefore, an object of this invention is to provide a alloy steel composition suitable for cryogenic service.
Anothex object is that the steel composition can be formulated without nickel.
Yet another object is that the steel composition can be formulated with a low manganese content.
Other objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of a preferred embodiment of the invention and the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention includes a ferritic cryogenic alloy steel of relatively low manganese content and a method of 9g impartin~ the cryoqenic properties to the steel. More particll-larly, the present alloy steel consists essenti~lly by weight of about 4-6% manganese, 0.02-0.06% carbon, 0.1-0.~ molybdenum, an~ the balance, iron and impuriti~s normally associated there-with.
The steel is characterized by a ductile-brittle tran-sition temperature below li~uid nitrogen (77K or -196C) and a Charp~ V-notch impact energy Cv greater ~han 50 f~-lb (67 joules) at liquid nitrogen temperatures. These cryogenic prop-erties are achieved by subjecting a steel of the aforementioned composition to a thermal cycling treatment and a subsequent temperinq. The carbon and molybdenum enhance the stability of retained gamma phase in the alloy and enhance the suppression of temper-embrittlement-type intergranular fracture. Further, the cryo~enic properties of the steel can be improved, while addin~ only slightly to the cost, by addition of up to about 3%
by wei~ht nickel.
Thus, broadly, the invent~on contemplates a cryogenic alloy steel having a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese,about 0.02-0.06 carbon, 0.1-0.4% molybdenum, and the balance iron and incidental impurities associated therewith, with the steel being character-ized by a ductile-brittle transition temperature below -196C and a Charpy V-notch impact energy value greater than about 67 ]oules at -196C.
The method of-imparting favourable cryogenic properties to the alloy steel is a thermal cycling treatment. The method ~ -includes the steps of forming a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese, about 0.02-0.06% carbon, 0.1-0.4~ molybdenum, and the balance iron and incidental impurities associated therewith, a first heating ~3-.
of the composition from a -temperature, which is below the characteristic temperature As at which the composition, initially having the low-temperature alpha structure, first begins to undergo two-phase decomposition through partial formation of the high temperature gamma structure, to a temperature, which is above the characteristic temperature Af above which the composition is austenitized in the sense that the transformation from the alpha structure to the gamma structure is essentially completed on heating, followed by a first cool-ing of the composition to a temperature below As. The com-position is heated a second time to a temperature above As and below Af, followed by a second cooling of the composition to a temperature below A , in turn, followed by a third heating of the composition to a temperature above Af, and a third cooling of the composition to a temperature below A , and finally followed by a fourth heating of the composi-tion to a temperature above As and below Af, and a fourth cooling of the composition to a temperature below As. The composition is then tempered at a temperature below As.
,~
-3a BRIEF DESCRIPTION OF THE DRAWINGS
Figure l is a heat treating cycle diagram.
Figure 2 is a composite graph illustrating the selec-tion o~ annealing temperatures from dila~omeric data.
Figure 3 is a composite graph of Charpy impact energy ~Cv) as a function of thermal cycling carried out in accord-ance with ~he present invention.
Figure 4 is a composite graph of the Charpy impact (Cv) at 77K (-196C) and the fracture appearance transition temperature (FATT) as a unction of carbon content for alloys of the present invention.
Figure S is a composite graph showing the yield strenqth (YS), tensile strength (TS), and the Charpy impact energy (Cv) as a function of nickel content for alloys of the present invention.
ETAILED D~SCRIPTION
The t~ermal cycling treatment results in an ultra-fine grain structure. This treatment is essentially a repeated alternation of ~ustenitization and (alpha ~ gamma) two phase decompositi~n. The type of thermal cycling treatment employed here is, described in detail in "The Use of Martensite Reversion in the Design of Touah Ferritic Cryogenic Steels" J. W. Morris, ~r., et a], Proceedings of thé First JIM International Sympo-sium on "New Aspects of Martensitic Transformation", May 10-12, 1976, The Japan Institute of Metals, Sendai, Japan. This type of thermal cycling treatment is also described in "Grain Refine-ment Through Thermal Cycling in an Fe-Ni-Ti Cryogenic Alloy" S.
Jin, et al, Metallurgical Transactions A, Vol. 6A ~1975), pp.
141-1~9.
` 30 The thermal cycling treatment includes alternate anneals o about one hour in between which the material is water-~uenched to a temperture below As and preferably to :. ., . :
~'6~i room temper~ture (air coolinq should be suitable, but slower).
In most cases, the anneal can be shortened to as little as 30 minutes or lengthened to as long as 2 hours without problems.
In the water quench, the temperature of the material is lowered sufficientlv to stabilize the structure, preferably to near amhient. A suitable cycle of anneals and quenches is shown graphirally in Figure 1, where the successive steps are labelled lA, lB, 2A, 2B, and T.
A method for selectinq the annealing temperatures used in steps lA, lB, 2A, and 2B from dilatometric data which indi-cate the phase transformation temperatures of the alloy on heating is illustrated graphically in Figure 2. ~wo reference temperatures are indicated graphically in Figure l and in Figure 2: (1) a temperature designated As, which is the approximate temperature at which an alloy initially having the low-temperature alpha structure first begins to undergo two-phase decomposition through partial formation of the high tem-perature gamma structure on heating, and (2) a second higher temperature designated Af above which the sample is austeni-tized in the sense that the transformation from the alphastructure to the gamma structure is essentially completed on heating. These reference temperatures wil] vary with the rate at which the alloy is heated but such variation is ~mall for the range of heating rates of interest in processing alloys of this type tfrom about ~0C/min to about 300C/min).
~ he variation of the reference temperatures, As and Af, with composition, i.e. with changes in manganese content~
is illustrated in Figure l and is small for minor change in manganese content. The variation of the reference temperatures with regard to adding 1-3% nickel to the base composition is il]ustrated in Figure 2 and is significantO
Based on Figures 1 and 2, the temperature for the first anneal (designated lA) is chosen to be slightly (about 40C) qreater than the temperature Af. The temperature for the second anneal (designated lB) is chosen to be less than the temperature Af. Good properties are obtained if the second-anneal temperature is taken to lie approximately mid-way between the reference temperatures As and Af. The temperature for the third anneal (designated 2A) i5 chosen to be slightly above and is, in practice, usually chosen to be slightly lower than the temperature of the first anneal. The temperature for the fourth anneal (designated 2B) is chosen so as to be below the temperature Af. Good properties are obtained if this temperature (step 2B) is identical to the temperature of the second anneal, ap~roximately mid-way between the re~erence tem-perat.ures As and Af.
The "final" tempering treatment (designated T or t), which is subsequent to the thermal cycling, introduces a small admixture of retained austenite. For the present steel, the preferred t~mpering conditions are a tempering temperature below about fiOOC, preferably about 540-600C and a tempering time of about 3-lh hours.
The atmosphere in contact with material during the di~ferent steps can be air. An inert atmosphere is preferred.
The following example is illustrative of the present invention.
EXAMPLE
A steel having the nominal composition: carbon - 0.038%, manqanese - 4.40%, molybdenum - 0.20~, silicon - 0.04~, sulfur -0.006%, and the balance iron, was subjected to different heat treatments and the mechanical properties investigated~ In Figure 3, results are shown for Charpy impact energy at -196C;
yield stress and tensile stress at the room temperature; and the retained austenite as a function of tempering time.
In the cases shown in Figure 3, the alloy was vacuum induction melted, homogenized at 1200C for 24 hours, forged into plate, and then solution annealed at 900C for 2 hours fol-lowed by air cooling before thermal cycling treatment. For this alloy As is about 700C and Af is abou~ 790C. The speci~ic thermal cycling treatment used consisted of, n sequence, a l-hour anneal (lA) at 820C, a water quench, a l-hour anneal (lB) at 740C, a water quench, a l-hour an~eal (2A) at 800C, a water quench, a l-hour anneal at either 740C (~B) or 710C (2b), a water quench, and a final tempering at 620C (t) or 590C (T) for 1-16 hours, followed by a water quench.
As seen in Figure 3, a very promising combination of toughness (~V) at -1~6C and room temperature strength was ob-tained by the heat treatment designated 2Bt and the use of a long tempering time (about 4-16 hours).
TEM (transmission electron microscopy) observation showed that the treatment yields an ultra-fine-grained micro-structure which consists of ultra-fine well-recovered equiaxed ferrite (~rain size about 0.5-1.0 micron) with a precipitated ~0 gamma phase at the ferrite grain boundaries and ferrite or mar-tensite lath boundaries.
The effect of carbon content on the properties of the alloy after the thermal treatment 2BT was also investigated. The results are illustrated in Figure 4; the Charpy impact energy (Cv) and the fracture appearance transition temperature (FATT) are plotted as a function of carbon content for two final tem-pering times, 4 hours and lfi hours. The properties of the alloy deteriorate if the carbon content is higher than about 0.06 per-cent by weight. Carbon contents near 0.04 yield good properties.
The effect of adding nickel to the base composition was also investiqated. The alloys used had nominal composition (in weight percent) manganese 5.0%, molybdenum 0.2%, carbon 0.06%, silicon 0.04%, sulur 0.006%, balance iron, with an addition of 0~ , or 3% nickel. The alloys were given the thermal cycling treatment described above, with the difference that for these nickel-bearing alloys the annealinq temperatures for steps lA, lB, 2A, and 2B were changed as shown graphically by the arrows in Figure 2. The resulting mechanical properties: yield strength (YS) at room temperature~ tensile strength (TS) at room tempera-ture, and Charpy impact energy (Cv) at 77K (-196C) are shown graphically in Figure 5. The room temperature yield strength was found to increase with nickel content while the Charpy impact toughness at 77K remained high. In the case of a 3% nickel addition the room temperature yield strength was llOksi while the Charpy impact energy at 77~ was 160 joules (120 ft-lb).
LOW Mn ALLOY STEEL FOR CRYOGENIC SERVICE
BACKGROtlND OF THE INVENTION
Field of the Invention . . _ This invention relates to an alloy steel composition, in particular, a low-maganese alloy steel composition suitable far cryoqenic applications and a method for preparing the com-position.
nescription of the Prior ~rt Due to dwindling natural gas supplies in this and other countries there is considerable interest in containment vessels for safely transporting liquefied natural gas (LNG) by ship and other transport. Because the boiling temperature of natural gas is in the cryogenic tgenerallY below about -80 to -100C) range, LN~. containers must be designed to avoid breakage due to pres-sure and crack development over a broad temperature range.
There is also the danger of a catastrophic explosion or fire, should the containment vessel fail.
At crvogenic temperatures, ordinary steel alloys lose much of their resilence and become very hrittle. A denominator of the steel alloys commonly specified for structural applica~
tians at LN~, and lower temperatures is a relatively high content of nickel. The nickel contributes significantly to good low tem~erature properties; but, is a relatively scarce metal and, thus, adds substantially to the cost. Recently, lower (5-6%) Ni steels have been introduced to reduce cost.
Storaqe systems for other liquefied gases, particularly nitrogen, oxygen, and liquid air, are also a significant market for cryogenic alloys. This market is different than that for LNG in that the safety standards are less stringent and a larger 7 ~
number of alloys compete with more emphasis placed on mate~ials cost.
Of the common alloying elements in steels, manganese is considered the most attractive substitute for nickel. Man-ganese ;s readily available, and, thus, relatively inexpensive, and has a metallurgical similarity to nickel in its effect on the microstructures and phase relationships of iron-based alloy~. Therefore, there has been considerable interest in the potential of Fe-Mn alIoys for cryogenic use.
Fe-12Mn (12% manganese) alloys have been made tough at 77K (-196C) by several methods: (1) a cold work plus temper-inq treatment, (2) controlled cooling through the martensite transformation, and (3) the addition of a minor amount of boron. However, although manganese is less expensive than ni~kel, it also adds to the cost of the steel, and, therefore, a lower manganese content would be advantageous.
Statement of the Objects Therefore, an object of this invention is to provide a alloy steel composition suitable for cryogenic service.
Anothex object is that the steel composition can be formulated without nickel.
Yet another object is that the steel composition can be formulated with a low manganese content.
Other objects, advantages and novel features of the invention will become apparent to those skilled in the art upon examination of the following detailed description of a preferred embodiment of the invention and the accompanying drawings.
SUMMARY OF THE INVENTION
The present invention includes a ferritic cryogenic alloy steel of relatively low manganese content and a method of 9g impartin~ the cryoqenic properties to the steel. More particll-larly, the present alloy steel consists essenti~lly by weight of about 4-6% manganese, 0.02-0.06% carbon, 0.1-0.~ molybdenum, an~ the balance, iron and impuriti~s normally associated there-with.
The steel is characterized by a ductile-brittle tran-sition temperature below li~uid nitrogen (77K or -196C) and a Charp~ V-notch impact energy Cv greater ~han 50 f~-lb (67 joules) at liquid nitrogen temperatures. These cryogenic prop-erties are achieved by subjecting a steel of the aforementioned composition to a thermal cycling treatment and a subsequent temperinq. The carbon and molybdenum enhance the stability of retained gamma phase in the alloy and enhance the suppression of temper-embrittlement-type intergranular fracture. Further, the cryo~enic properties of the steel can be improved, while addin~ only slightly to the cost, by addition of up to about 3%
by wei~ht nickel.
Thus, broadly, the invent~on contemplates a cryogenic alloy steel having a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese,about 0.02-0.06 carbon, 0.1-0.4% molybdenum, and the balance iron and incidental impurities associated therewith, with the steel being character-ized by a ductile-brittle transition temperature below -196C and a Charpy V-notch impact energy value greater than about 67 ]oules at -196C.
The method of-imparting favourable cryogenic properties to the alloy steel is a thermal cycling treatment. The method ~ -includes the steps of forming a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese, about 0.02-0.06% carbon, 0.1-0.4~ molybdenum, and the balance iron and incidental impurities associated therewith, a first heating ~3-.
of the composition from a -temperature, which is below the characteristic temperature As at which the composition, initially having the low-temperature alpha structure, first begins to undergo two-phase decomposition through partial formation of the high temperature gamma structure, to a temperature, which is above the characteristic temperature Af above which the composition is austenitized in the sense that the transformation from the alpha structure to the gamma structure is essentially completed on heating, followed by a first cool-ing of the composition to a temperature below As. The com-position is heated a second time to a temperature above As and below Af, followed by a second cooling of the composition to a temperature below A , in turn, followed by a third heating of the composition to a temperature above Af, and a third cooling of the composition to a temperature below A , and finally followed by a fourth heating of the composi-tion to a temperature above As and below Af, and a fourth cooling of the composition to a temperature below As. The composition is then tempered at a temperature below As.
,~
-3a BRIEF DESCRIPTION OF THE DRAWINGS
Figure l is a heat treating cycle diagram.
Figure 2 is a composite graph illustrating the selec-tion o~ annealing temperatures from dila~omeric data.
Figure 3 is a composite graph of Charpy impact energy ~Cv) as a function of thermal cycling carried out in accord-ance with ~he present invention.
Figure 4 is a composite graph of the Charpy impact (Cv) at 77K (-196C) and the fracture appearance transition temperature (FATT) as a unction of carbon content for alloys of the present invention.
Figure S is a composite graph showing the yield strenqth (YS), tensile strength (TS), and the Charpy impact energy (Cv) as a function of nickel content for alloys of the present invention.
ETAILED D~SCRIPTION
The t~ermal cycling treatment results in an ultra-fine grain structure. This treatment is essentially a repeated alternation of ~ustenitization and (alpha ~ gamma) two phase decompositi~n. The type of thermal cycling treatment employed here is, described in detail in "The Use of Martensite Reversion in the Design of Touah Ferritic Cryogenic Steels" J. W. Morris, ~r., et a], Proceedings of thé First JIM International Sympo-sium on "New Aspects of Martensitic Transformation", May 10-12, 1976, The Japan Institute of Metals, Sendai, Japan. This type of thermal cycling treatment is also described in "Grain Refine-ment Through Thermal Cycling in an Fe-Ni-Ti Cryogenic Alloy" S.
Jin, et al, Metallurgical Transactions A, Vol. 6A ~1975), pp.
141-1~9.
` 30 The thermal cycling treatment includes alternate anneals o about one hour in between which the material is water-~uenched to a temperture below As and preferably to :. ., . :
~'6~i room temper~ture (air coolinq should be suitable, but slower).
In most cases, the anneal can be shortened to as little as 30 minutes or lengthened to as long as 2 hours without problems.
In the water quench, the temperature of the material is lowered sufficientlv to stabilize the structure, preferably to near amhient. A suitable cycle of anneals and quenches is shown graphirally in Figure 1, where the successive steps are labelled lA, lB, 2A, 2B, and T.
A method for selectinq the annealing temperatures used in steps lA, lB, 2A, and 2B from dilatometric data which indi-cate the phase transformation temperatures of the alloy on heating is illustrated graphically in Figure 2. ~wo reference temperatures are indicated graphically in Figure l and in Figure 2: (1) a temperature designated As, which is the approximate temperature at which an alloy initially having the low-temperature alpha structure first begins to undergo two-phase decomposition through partial formation of the high tem-perature gamma structure on heating, and (2) a second higher temperature designated Af above which the sample is austeni-tized in the sense that the transformation from the alphastructure to the gamma structure is essentially completed on heating. These reference temperatures wil] vary with the rate at which the alloy is heated but such variation is ~mall for the range of heating rates of interest in processing alloys of this type tfrom about ~0C/min to about 300C/min).
~ he variation of the reference temperatures, As and Af, with composition, i.e. with changes in manganese content~
is illustrated in Figure l and is small for minor change in manganese content. The variation of the reference temperatures with regard to adding 1-3% nickel to the base composition is il]ustrated in Figure 2 and is significantO
Based on Figures 1 and 2, the temperature for the first anneal (designated lA) is chosen to be slightly (about 40C) qreater than the temperature Af. The temperature for the second anneal (designated lB) is chosen to be less than the temperature Af. Good properties are obtained if the second-anneal temperature is taken to lie approximately mid-way between the reference temperatures As and Af. The temperature for the third anneal (designated 2A) i5 chosen to be slightly above and is, in practice, usually chosen to be slightly lower than the temperature of the first anneal. The temperature for the fourth anneal (designated 2B) is chosen so as to be below the temperature Af. Good properties are obtained if this temperature (step 2B) is identical to the temperature of the second anneal, ap~roximately mid-way between the re~erence tem-perat.ures As and Af.
The "final" tempering treatment (designated T or t), which is subsequent to the thermal cycling, introduces a small admixture of retained austenite. For the present steel, the preferred t~mpering conditions are a tempering temperature below about fiOOC, preferably about 540-600C and a tempering time of about 3-lh hours.
The atmosphere in contact with material during the di~ferent steps can be air. An inert atmosphere is preferred.
The following example is illustrative of the present invention.
EXAMPLE
A steel having the nominal composition: carbon - 0.038%, manqanese - 4.40%, molybdenum - 0.20~, silicon - 0.04~, sulfur -0.006%, and the balance iron, was subjected to different heat treatments and the mechanical properties investigated~ In Figure 3, results are shown for Charpy impact energy at -196C;
yield stress and tensile stress at the room temperature; and the retained austenite as a function of tempering time.
In the cases shown in Figure 3, the alloy was vacuum induction melted, homogenized at 1200C for 24 hours, forged into plate, and then solution annealed at 900C for 2 hours fol-lowed by air cooling before thermal cycling treatment. For this alloy As is about 700C and Af is abou~ 790C. The speci~ic thermal cycling treatment used consisted of, n sequence, a l-hour anneal (lA) at 820C, a water quench, a l-hour anneal (lB) at 740C, a water quench, a l-hour an~eal (2A) at 800C, a water quench, a l-hour anneal at either 740C (~B) or 710C (2b), a water quench, and a final tempering at 620C (t) or 590C (T) for 1-16 hours, followed by a water quench.
As seen in Figure 3, a very promising combination of toughness (~V) at -1~6C and room temperature strength was ob-tained by the heat treatment designated 2Bt and the use of a long tempering time (about 4-16 hours).
TEM (transmission electron microscopy) observation showed that the treatment yields an ultra-fine-grained micro-structure which consists of ultra-fine well-recovered equiaxed ferrite (~rain size about 0.5-1.0 micron) with a precipitated ~0 gamma phase at the ferrite grain boundaries and ferrite or mar-tensite lath boundaries.
The effect of carbon content on the properties of the alloy after the thermal treatment 2BT was also investigated. The results are illustrated in Figure 4; the Charpy impact energy (Cv) and the fracture appearance transition temperature (FATT) are plotted as a function of carbon content for two final tem-pering times, 4 hours and lfi hours. The properties of the alloy deteriorate if the carbon content is higher than about 0.06 per-cent by weight. Carbon contents near 0.04 yield good properties.
The effect of adding nickel to the base composition was also investiqated. The alloys used had nominal composition (in weight percent) manganese 5.0%, molybdenum 0.2%, carbon 0.06%, silicon 0.04%, sulur 0.006%, balance iron, with an addition of 0~ , or 3% nickel. The alloys were given the thermal cycling treatment described above, with the difference that for these nickel-bearing alloys the annealinq temperatures for steps lA, lB, 2A, and 2B were changed as shown graphically by the arrows in Figure 2. The resulting mechanical properties: yield strength (YS) at room temperature~ tensile strength (TS) at room tempera-ture, and Charpy impact energy (Cv) at 77K (-196C) are shown graphically in Figure 5. The room temperature yield strength was found to increase with nickel content while the Charpy impact toughness at 77K remained high. In the case of a 3% nickel addition the room temperature yield strength was llOksi while the Charpy impact energy at 77~ was 160 joules (120 ft-lb).
Claims (8)
1. A cryogenic alloy steel having a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese, about 0.02-0.06% carbon, 0.1-0.4% molybdenum, and the balance iron and incidental impurities associated therewith, said steel being characterized by a ductile-brittle transition temperature below -196°C and a Charpy V-notch impact energy value greater than about 67 joules at -196°C.
2. The steel according to claim 1 wherein favorable cryogenic characteristics are achieved by subjecting said composition to a thermal cycling treatment consisting essentially of a repeated alternation of austenitization and (alpha + gamma) two phase decomposition and a subsequent tempering treatment at a temperature below about 600°C for about 3-16 hours.
3. A method of imparting favorable cryogenic properties to an alloy steel comprising the steps of:
a. forming a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese, about 0.02-0.06%
carbon, 0.1-0.4% molybdenum, and the balance iron and incidental impurities associated therewith;
b. a first heating of the composition from a temperature, which is below the charac-teristic temperature As at which the composition, initially having the low-temperature alpha structure, first begins to undergo two-phase decomposition through partial formation of the high temperature gamma structure, to a temperature, which is above the characteristic temperature Af above which the composition is austenitized in the sense that the transformation from the alpha structure to the gamma structure is essentially completed on heating;
c. a first cooling of the composition to a temperature below As;
d. a second heating of the composition to a temperature above As and below Af;
e. a second cooling of the composition to a temperature below As;
f. a third heating of the composition to a temperature above Af;
g. a third cooling of the composition to a temperature below As;
h. a fourth heating of the composition to a temperature above As and below Af;
i. a fourth cooling of the composition to a temperature below As; and j. a tempering of the composition at a temperature below As.
a. forming a composition which is essentially free of nickel and consisting essentially of about 4-6% manganese, about 0.02-0.06%
carbon, 0.1-0.4% molybdenum, and the balance iron and incidental impurities associated therewith;
b. a first heating of the composition from a temperature, which is below the charac-teristic temperature As at which the composition, initially having the low-temperature alpha structure, first begins to undergo two-phase decomposition through partial formation of the high temperature gamma structure, to a temperature, which is above the characteristic temperature Af above which the composition is austenitized in the sense that the transformation from the alpha structure to the gamma structure is essentially completed on heating;
c. a first cooling of the composition to a temperature below As;
d. a second heating of the composition to a temperature above As and below Af;
e. a second cooling of the composition to a temperature below As;
f. a third heating of the composition to a temperature above Af;
g. a third cooling of the composition to a temperature below As;
h. a fourth heating of the composition to a temperature above As and below Af;
i. a fourth cooling of the composition to a temperature below As; and j. a tempering of the composition at a temperature below As.
4. The method according to claim 3 wherein the temperature to which the composition is cooled in the first cooling is about room temperature.
5. The method according to claim 3 wherein the temperature to which the composition is cooled in the second cooling is about room temperature.
6. The method according to claim 3 wherein the temperature to which the composition is heated in the first heating is within about 40°C of Af.
7. The method according to claim 3 wherein the temperature to which the composition is heated in the second heating is about midway between As and Af.
8. The method according to claim 3 wherein the tempering is at a temperature between about 540°C and 600°C and for a period between about 3 and 15 hours.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/066,106 US4257808A (en) | 1979-08-13 | 1979-08-13 | Low Mn alloy steel for cryogenic service and method of preparation |
| US066,106 | 1987-06-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1171699A true CA1171699A (en) | 1984-07-31 |
Family
ID=22067281
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000357401A Expired CA1171699A (en) | 1979-08-13 | 1980-07-31 | Low mn alloy steel for cryogenic service |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US4257808A (en) |
| JP (1) | JPS5629654A (en) |
| CA (1) | CA1171699A (en) |
| DE (1) | DE3030652A1 (en) |
| FR (1) | FR2463193B1 (en) |
| GB (1) | GB2058132B (en) |
| NO (1) | NO153930C (en) |
| SE (1) | SE441838B (en) |
Families Citing this family (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3432337A1 (en) * | 1984-09-03 | 1986-03-13 | Hoesch Stahl AG, 4600 Dortmund | METHOD FOR PRODUCING A STEEL AND USE THEREOF |
| TW444109B (en) * | 1997-06-20 | 2001-07-01 | Exxon Production Research Co | LNG fuel storage and delivery systems for natural gas powered vehicles |
| TW359736B (en) * | 1997-06-20 | 1999-06-01 | Exxon Production Research Co | Systems for vehicular, land-based distribution of liquefied natural gas |
| TW396253B (en) * | 1997-06-20 | 2000-07-01 | Exxon Production Research Co | Improved system for processing, storing, and transporting liquefied natural gas |
| TW396254B (en) | 1997-06-20 | 2000-07-01 | Exxon Production Research Co | Pipeline distribution network systems for transportation of liquefied natural gas |
| TW436597B (en) * | 1997-12-19 | 2001-05-28 | Exxon Production Research Co | Process components, containers, and pipes suitable for containign and transporting cryogenic temperature fluids |
| AU2002365596B2 (en) | 2001-11-27 | 2007-08-02 | Exxonmobil Upstream Research Company | CNG fuel storage and delivery systems for natural gas powered vehicles |
| US6852175B2 (en) * | 2001-11-27 | 2005-02-08 | Exxonmobil Upstream Research Company | High strength marine structures |
| US7063752B2 (en) * | 2001-12-14 | 2006-06-20 | Exxonmobil Research And Engineering Co. | Grain refinement of alloys using magnetic field processing |
| US7655160B2 (en) | 2005-02-23 | 2010-02-02 | Electromagnetics Corporation | Compositions of matter: system II |
| US8932207B2 (en) | 2008-07-10 | 2015-01-13 | Covidien Lp | Integrated multi-functional endoscopic tool |
| WO2010051395A1 (en) * | 2008-10-30 | 2010-05-06 | Electromagnetics Corporation | Composition of matter tailoring: system ia |
| KR101271974B1 (en) | 2010-11-19 | 2013-06-07 | 주식회사 포스코 | High-strength steel having excellent cryogenic toughness and method for production thereof |
| US10655196B2 (en) | 2011-12-27 | 2020-05-19 | Posco | Austenitic steel having excellent machinability and ultra-low temperature toughness in weld heat-affected zone, and method of manufacturing the same |
| KR101543916B1 (en) | 2013-12-25 | 2015-08-11 | 주식회사 포스코 | Steels for low temperature services having superior deformed surface quality and method for production thereof |
| AU2017353259B2 (en) * | 2016-11-02 | 2022-12-22 | Salzgitter Flachstahl Gmbh | Medium-manganese steel product for low-temperature use and method for the production thereof |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US28645A (en) * | 1860-06-12 | Claw-bab | ||
| GB440894A (en) * | 1933-07-20 | 1936-01-08 | Krupp Ag | Improved constructional parts |
| US2516125A (en) * | 1949-04-11 | 1950-07-25 | Irvin R Kramer | Alloy steel |
| DE1239481B (en) * | 1960-07-18 | 1967-04-27 | Mannesmann Ag | Use of a high-strength structural steel as a material for welded objects with good low-temperature properties |
| JPS4935485B1 (en) * | 1964-06-22 | 1974-09-24 | ||
| US3619305A (en) * | 1968-02-26 | 1971-11-09 | Explosifs Prod Chim | Explosive compositions containing expanded ammonium nitrate in crystalline form and method of preparing same |
| USRE28645E (en) * | 1968-11-18 | 1975-12-09 | Method of heat-treating low temperature tough steel | |
| CS155664B1 (en) * | 1970-10-06 | 1974-05-30 | ||
| CA958290A (en) * | 1970-11-06 | 1974-11-26 | Head, Wrightson And Company Limited | Chromised ferrous metal article and a process for the production thereof |
| US4047979A (en) * | 1976-10-08 | 1977-09-13 | United States Steel Corporation | Heat treatment for improving the toughness of high manganese steels |
| JPS5495916A (en) * | 1978-01-11 | 1979-07-28 | Sumitomo Metal Ind Ltd | Manufactue of ultra low carbon, fine grain, high tensile steel with superior toughness |
| US4162158A (en) * | 1978-12-28 | 1979-07-24 | The United States Of America As Represented By The United States Department Of Energy | Ferritic Fe-Mn alloy for cryogenic applications |
-
1979
- 1979-08-13 US US06/066,106 patent/US4257808A/en not_active Expired - Lifetime
-
1980
- 1980-07-31 CA CA000357401A patent/CA1171699A/en not_active Expired
- 1980-08-04 GB GB8025416A patent/GB2058132B/en not_active Expired
- 1980-08-11 SE SE8005659A patent/SE441838B/en not_active IP Right Cessation
- 1980-08-13 NO NO802415A patent/NO153930C/en unknown
- 1980-08-13 JP JP11157380A patent/JPS5629654A/en active Granted
- 1980-08-13 DE DE19803030652 patent/DE3030652A1/en not_active Withdrawn
- 1980-08-13 FR FR8017889A patent/FR2463193B1/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB2058132A (en) | 1981-04-08 |
| FR2463193A1 (en) | 1981-02-20 |
| GB2058132B (en) | 1984-02-29 |
| FR2463193B1 (en) | 1986-07-11 |
| SE8005659L (en) | 1981-02-14 |
| NO153930C (en) | 1986-06-18 |
| JPS5629654A (en) | 1981-03-25 |
| SE441838B (en) | 1985-11-11 |
| NO153930B (en) | 1986-03-10 |
| NO802415L (en) | 1981-02-16 |
| US4257808A (en) | 1981-03-24 |
| JPS6349737B2 (en) | 1988-10-05 |
| DE3030652A1 (en) | 1981-03-26 |
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